/********************************************************************************
 * Copyright (c) 2021,2022 Contributors to the CatenaX (ng) GitHub Organisation
 *
 * See the NOTICE file(s) distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Apache License, Version 2.0 which is available at
 * https://www.apache.org/licenses/LICENSE-2.0.
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 * SPDX-License-Identifier: Apache-2.0
 ********************************************************************************/

import { BehaviorSubject, Observable } from 'rxjs';
import { delay, distinctUntilChanged } from 'rxjs/operators';

export class State<T> {
  private readonly store$: BehaviorSubject<T>;
  private readonly initialValue: T;
  private stateValue: T;

  constructor(initialValue: T) {
    this.initialValue = initialValue;
    this.stateValue = initialValue;
    this.store$ = new BehaviorSubject<T>(initialValue);
  }

  public get observable(): Observable<T> {
    return this.store$.asObservable().pipe(distinctUntilChanged(), delay(0));
  }

  public get snapshot(): T {
    return this.stateValue;
  }

  public update(value: T): void {
    this.stateValue = value;
    this.store$.next(this.stateValue);
  }

  public reset(): void {
    this.stateValue = this.initialValue;
    this.store$.next(this.stateValue);
  }
}
